U.S. patent number 10,994,989 [Application Number 16/476,455] was granted by the patent office on 2021-05-04 for method for producing a microelectromechanical component and wafer system.
This patent grant is currently assigned to Robert Bosch GmbH. The grantee listed for this patent is Robert Bosch GmbH. Invention is credited to Vijaye Rajaraman, Eckart Schellkes.
View All Diagrams
United States Patent |
10,994,989 |
Rajaraman , et al. |
May 4, 2021 |
Method for producing a microelectromechanical component and wafer
system
Abstract
A method for producing a microelectromechanical component as
well as a wafer system includes steps of: providing a first wafer
having a plurality of microelectromechanical base elements; forming
a respective container structure on the microelectromechanical base
elements at the wafer level; and disposing an oil or a gel within
the container structures.
Inventors: |
Rajaraman; Vijaye (Reutlingen,
DE), Schellkes; Eckart (Taipei, TW) |
Applicant: |
Name |
City |
State |
Country |
Type |
Robert Bosch GmbH |
Stuttgart |
N/A |
DE |
|
|
Assignee: |
Robert Bosch GmbH (Stuttgart,
DE)
|
Family
ID: |
1000005528677 |
Appl.
No.: |
16/476,455 |
Filed: |
December 15, 2017 |
PCT
Filed: |
December 15, 2017 |
PCT No.: |
PCT/EP2017/083069 |
371(c)(1),(2),(4) Date: |
July 08, 2019 |
PCT
Pub. No.: |
WO2018/127385 |
PCT
Pub. Date: |
July 12, 2018 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20200055727 A1 |
Feb 20, 2020 |
|
Foreign Application Priority Data
|
|
|
|
|
Jan 9, 2017 [DE] |
|
|
10 2017 200 162.3 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B81C
1/00285 (20130101); B81C 2203/0145 (20130101); B81B
2203/0127 (20130101); B81B 2201/0264 (20130101); B81B
2207/012 (20130101); B81C 2203/031 (20130101) |
Current International
Class: |
H01L
21/00 (20060101); G01L 9/00 (20060101); B81C
1/00 (20060101) |
Field of
Search: |
;257/416-420
;438/50-53 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
102009001969 |
|
Jul 2010 |
|
DE |
|
102010030960 |
|
Dec 2012 |
|
DE |
|
2423656 |
|
Feb 2012 |
|
EP |
|
2016191699 |
|
Nov 2016 |
|
JP |
|
Other References
International Search Report for PCT/EP2017/083069, dated Mar. 8,
2018. cited by applicant.
|
Primary Examiner: Lee; Calvin
Attorney, Agent or Firm: Norton Rose Fulbright US LLP
Messina; Gerard
Claims
What is claimed is:
1. A method for producing a microelectromechanical component, the
method comprising: providing a first wafer with a plurality of
microelectromechanical base elements, wherein the
microelectromechanical base elements are pressure sensors that each
includes a respective pressure sensor diaphragm; while the
plurality of microelectromechanical base elements are on the first
wafer, connecting a second wafer to the first wafer to attach at
least one microelectromechanical or micromechanical structure on
the microelectromechanical base elements, thereby forming
respective container structures around or on respective ones of the
microelectromechanical base elements, wherein the respective
container structures are each disposed and developed such that an
outer side of the pressure sensor diaphragm of the respective base
elements is covered by an oil or gel disposed in the respective
container structures; and disposing the oil or a gel within the
container structures.
2. The method of claim 1, wherein: the microelectromechanical base
elements are electrically and/or mechanically connected to the
first wafer; and the method further comprises: forming a super
container structure around the microelectromechanical base elements
and their the respective container structures; and disposing
another gel in the super container structure.
3. The method of claim 1, wherein, within the container structure,
in addition to the oil or the gel, a respective
application-specific integrated circuit (ASIC) is disposed and
connected electrically and mechanically to the respective
microelectromechanical base element.
4. The method of claim 1, wherein: the disposing is of the oil; the
disposing of the oil is performed by filling the oil into a filler
opening in the container structure; and after disposing the oil the
filler opening is closed.
5. The method of claim 1, wherein the second wafer is a glass
wafer, from which glass covers are formed as the container
structures for the microelectromechanical base elements on the
first wafer.
6. The method of claim 5, wherein the second wafer is connected to
the first wafer by anodic wafer bondings.
7. The method of claim 1, wherein the forming of the respective
container structures includes a simultaneous attachment of the
container structures to their respective base elements.
8. The method of claim 7, wherein the container structures are
microelectromechanical container structures.
9. The method of claim 7, wherein the contained structures are
micromechanical container structures.
10. A wafer system comprising: a first wafer; a plurality of
microelectromechanical base elements on the first wafer, wherein
the microelectromechanical base elements are pressure sensors that
each includes a respective pressure sensor diaphragm; container
structures disposed around or on respective ones of the
microelectromechanical base elements, wherein the container
structures are formed by a second wafer connected to the first
wafer, wherein the each container structure is disposed and
developed such that an outer side of the respective pressure sensor
diaphragm of the respective base element is covered by an oil or
gel disposed in the respective container structures; and the oil or
a gel disposed in the container structures.
11. The wafer system of claim 10, wherein: the
microelectromechanical base elements are electrically and/or
mechanically connected to the first wafer; and the wafer system
further comprises: a super container structure around the
microelectromechanical base elements and their the respective
container structures; and disposing another gel in the super
container structure.
12. A microelectromechanical component comprising: a wafer; at
least one microelectromechanical base element disposed on the
wafer, the at least one microelectromechanical base element being a
pressure sensor that includes a respective pressure sensor
diaphragm; at least one first container structure, including a
respective first container structure around or on a respective one
of the at least one microelectromechanical base element; an oil or
a gel disposed in the at least one first container structure,
wherein the first container structure is disposed and developed
such that an outer side of the pressure sensor diaphragm of the
base element is covered by the oil or gel disposed in the first
container structure; a second container structure disposed on the
wafer around the at least one microelectromechanical base element
and the at least one first container structure; and another oil or
gel disposed in the second container structure and around the at
least one first container structure.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is the national stage of International Pat.
App. No. PCT/EP2017/083069 filed Dec. 15, 2017, and claims priority
under 35 U.S.C. .sctn. 119 to DE 10 2017 200 162.3, filed in the
Federal Republic of Germany on Jan. 9, 2017, the content of each of
which are incorporated herein by reference in their entireties.
FIELD OF THE INVENTION
The present invention relates to a method for producing a
microelectromechanical component and to a wafer system.
BACKGROUND
Microelectromechanical components often require protection against
dust, particles, moisture, exhaust gases, and/or other corrosive or
aggressive media. This applies especially to microelectromechanical
sensor devices that must be exposed to an environment in order to
fulfill their function. For example, microelectromechanical
pressure sensors have at least one deformable, pressure-sensitive
diaphragm, the so-called pressure sensor diaphragm, which is
typically exposed to an environment containing a corrosive medium.
Pressure signals are detected and subsequently evaluated using a
pressure sensor circuit, for example a bridge circuit, on the
pressure sensor diaphragm. The sensitive pressure sensor diaphragm
must be exposed in some manner to sound waves from the
environment.
A known solution from the related art is to insulate a finished
microelectromechanical pressure sensor element at the packaging
level using a gel or an oil. Physical signals such as sound waves,
for example, propagate through the oil or the gel to reach the
pressure sensor diaphragm, for example. The oil or gel thus does
not interfere with the measurement, while providing at the same
time an insulation of the pressure sensor diaphragm from the
environment. An exemplary method for hermetically sealing a MEMS
(microelectromechanical system) package is described in U.S. Pat.
No. 6,946,728 B2 for example.
U.S. Pat. No. 6,432,737 B1 describes a method for producing gel
containers around pressure sensor elements on a wafer. A form tool
is brought into contact with the pressure sensor elements and an
encapsulation material is conducted around the pressure sensor
elements so that after removal of the form tool, gel containers are
formed by the hardened encapsulation material in the area of the
pressure sensor elements, which can then be filled with a gel.
US 2012/0306031 A1 describes a method for producing gel containers
around piezoresistive transducers, in which first lateral walls are
disposed around the transducers and thereupon lids are glued onto
the lateral walls using an adhesive. The adhesive is hardened by
heating in an oven.
US 2014/0117474 A1 describes a microelectromechanical pressure
sensor element having a gel filling, in which a tubular element,
which is largely free of gel, is situated above the sensor
diaphragm of the pressure sensor element.
SUMMARY
The present invention is directed to a microelectromechanical
component, a wafer system, and a method for production thereof.
According to an example embodiment of the present invention, a
method for producing a microelectromechanical component includes:
providing a first wafer having a plurality of
microelectromechanical base elements; forming a respective
container structure around the micromechanical base elements, on
the microelectromechanical base elements or at the
microelectromechanical base elements, in particular at the wafer
level; and disposing an oil or a gel within the container
structures, in particular at the wafer level.
A microelectromechanical base element is to be understood as a
microelectromechanical element that represents a component part of
the microelectromechanical component to be produced. The
microelectromechanical base element can be a MEMS structure for
example, that is, a microelectromechanical system, in particular a
MEMS sensor, very particularly a MEMS pressure sensor, an
application-specific integrated circuit (ASIC) and the like.
A container structure is to be understood as any structure that is
capable of receiving either an oil or a gel and of keeping it in a
specific location. Examples of container structures are for example
closed annular structures, having a circular or rectangular cross
section for example, covers or hoods, which form a closed space
together with the wafer, which is filled at least partially or
completely with oil or gel, hollowed-out rectangular
parallelepipeds and the like.
That a method step is to be performed at the wafer level is to be
understood in particular as that the corresponding method step can
be performed simultaneously on a multitude of
microelectromechanical base elements on a wafer before the
individual microelectromechanical base elements are separated from
the wafer.
Processing at the wafer level thus differs from processing at the
package level, at which already separated microelectromechanical
components are individually packaged, which usually entails a
greater effort. Instead of processing at the wafer level, it is
alternatively also possible to work with chip-scale packages.
In addition, a microelectromechanical component is provided,
including a wafer, on which at least one microelectromechanical
base element is disposed or attached. The microelectromechanical
base element can be in particular a MEMS pressure sensor. A first
container structure is developed around the microelectromechanical
base element or on the microelectromechanical base element, in
which an oil or gel is disposed. Around the microelectromechanical
base element and the container structure, a second container
structure is disposed or attached on the wafer. Another oil or gel
is disposed in the additional container structure.
If the microelectromechanical base element is a MEMS sensor having
a pressure sensor diaphragm, the oil or gel is preferably disposed
in the first container structure in such a way that the pressure
sensor diaphragm is covered by it, and moreover the oil or gel in
the second container structure is preferably disposed in such a way
that the base element and/or the first container structure is/are
covered by it.
Furthermore, a wafer system is provided, including a first wafer
having a plurality of microelectromechanical base elements and
container structures, which are disposed around the
microelectromechanical base elements or on the
microelectromechanical base elements, an oil or a gel being
respectively disposed in the container structures. Preferably, a
respective container structure is disposed on each of the
microelectromechanical base elements. The same oil or the same gel,
different oils and/or different gels can be disposed in the
individual container structures so that even at the wafer level it
is possible to produce different microelectromechanical components
on one and the same wafer.
The wafer can be in particular a silicon wafer, which can be
developed having electrical contacts such as printed conductor
tracks, through-hole contacts and the like.
The present invention advantageously allows for producing
microelectromechanical components at the wafer level, which are at
least in areas protected against environmental influences by
container structures filled with an oil or a gel. It is thus
possible to produce microelectromechanical components in a
particularly robust manner and at the same time with particularly
small technical effort. This is particularly advantageous for
microelectromechanical pressure sensor systems. The
microelectromechanical base element can advantageously be a MEMS
pressure sensor having a cavity, which is separated from the
environment by a pressure sensor diaphragm. The container structure
can be developed in such a way that it encloses the pressure sensor
diaphragm, or another diaphragm, laterally, which makes it possible
to dispose the oil or the gel above the pressure sensor diaphragm
and hold it there. The pressure sensor diaphragm is thus shielded
against dust, particles, moisture, exhaust gases, and/or other
corrosive and/or aggressive media.
Furthermore, it becomes possible to shield for example metallic
bonding pads on MEMS components or MEMS base elements or ASICs
against direct environmental influences such as from corrosive
fluids, for example.
According to an example embodiment, the formation of the container
structures comprises the steps of: forming a polymer layer on the
microelectromechanical base elements; and patterning the polymer
layer. Instead of one polymer layer, it is also possible to form
and pattern multiple polymer layers.
The patterning of the polymer layer can be performed for example by
photolithography and/or by etching. In this manner, the container
structures can be produced with small technical effort using fully
developed methods known in the related art, which allows for quick,
safe, and cost-effective processing.
According to an example embodiment, the formation of the container
structures includes the step of attaching at least one
microelectromechanical and/or micromechanical structure, e.g., a
cap, on the microelectromechanical base elements. The attachment of
the at least one microelectromechanical or micromechanical
structure on the microelectromechanical base elements can be
performed for example by adhesive wafer bonding, in particular when
using a wafer made of silicon or of glass. Moreover, in particular
when using a glass wafer, it is possible to perform anodic wafer
bonding. The glass wafer can be in particular a glass-cap wafer,
that is, a glass wafer that is designed for providing glass caps
for a multitude of microelectromechanical base elements on the
wafer.
Accordingly, the attachment of the at least one
microelectromechanical or micromechanical structure on the
microelectromechanical base elements can be performed preferably by
connecting a second wafer with the first wafer. Preferably,
respectively one microelectromechanical or micromechanical
structure is attached on each microelectromechanical base element
so that each microelectromechanical base element is developed
having its own container structure. Preferably, the attachment of
respectively one microelectromechanical or micromechanical
structure on each of the microelectromechanical base elements thus
occurs simultaneously or essentially simultaneously.
The attachment of the at least one microelectromechanical or
micromechanical structure on the microelectromechanical base
elements can furthermore be performed by attaching an annular
structure, for example made from a plastic, a glass or a metal, on
the microelectromechanical base elements or around the
microelectromechanical base elements by using known adhesion
methods.
According to an example embodiment, the oil is placed by filling
the oil into a filler opening developed in the container structure,
the filler opening being closed after placement of the oil in the
container structure, whereupon the container structure has no
further openings to the outside world and the oil is thus
advantageously enclosed by the container structure.
According to an example embodiment, the microelectromechanical base
elements are pressure sensors, that is, MEMS pressure sensors,
which are each developed having a pressure sensor diaphragm. The
respective container structure can be situated and developed in
such a way that an outer side of the pressure sensor diaphragm is
covered by the oil or gel disposed in the container structure. Thus
it is possible to protect the often sensitive pressure sensor
diaphragm and bonding pads situated on the pressure sensor
diaphragm against environmental influences.
According to yet an example embodiment, an application-specific
integrated circuit, ASIC, is situated within the container
structure in addition to the oil or the gel and is connected
electrically and/or mechanically to the microelectromechanical base
element. In this manner, the container structure and the oil or gel
disposed in it are able to protect also the bonding pads,
conductors or contacts on the application-specific integrated
circuit or connections of the application-specific integrated
circuit to the microelectromechanical base element against
environmental influences.
According to an example embodiment, the microelectromechanical base
elements are connected electrically and/or mechanically to the
wafer. Advantageously, another container structure, in which
another gel is disposed, can be situated around the
microelectromechanical base elements with their respectively
associated container structures. This makes it possible for example
to select different gels and situate them successively for
protecting the base elements, which gels are adapted to the
respective application. Furthermore, contacts, conductors, and
connections such as for example bonding wires between the
microelectromechanical base element and for example an
application-specific integrated circuit on the same wafer can
likewise be shielded by gel from the outside world.
In the following, the present invention is explained in greater
detail with reference to the example embodiments shown in the
schematic figures of the drawings in which, unless indicated
otherwise, identical or functionally equivalent elements and
devices have been provided with the same reference symbols. The
numbering of method steps is used for clarity and generally is in
particular not intended to imply a specific sequence in time,
unless indicated otherwise. In particular, it is also possible to
carry out multiple method steps at the same time.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is flowchart that illustrates a method for producing a
microelectromechanical component according to an example embodiment
of the present invention.
FIG. 2 is flowchart that illustrates a method for producing a
microelectromechanical component according to another example
embodiment of the present invention.
FIGS. 3a-3c are schematic cross-sectional representations of
microelectromechanical components according to example embodiments
of the present invention.
FIG. 4 is flowchart that illustrates a method for producing a
microelectromechanical component according to another example
embodiment of the present invention.
FIGS. 5a-5c are schematic cross-sectional representations of
microelectromechanical components according to further example
embodiments of the present invention.
FIG. 6 is flowchart that illustrates a method for producing a
microelectromechanical component according to yet another example
embodiment of the present invention.
FIG. 7 is a schematic cross-sectional representation of a
microelectromechanical component according to an example embodiment
of the present invention.
FIG. 8 is flowchart that illustrates a method for producing a
microelectromechanical component according to yet another example
embodiment of the present invention.
FIGS. 9a-9d are schematic cross-sectional representations of
microelectromechanical components according to further example
embodiments of the present invention.
FIGS. 10a-10c are schematic sectional representations of a
microelectromechanical component according to another example
embodiment of the present invention.
FIGS. 11a-11c are schematic sectional representations for
explaining a production method for the microelectromechanical
component shown in FIGS. 10a-10c.
FIGS. 12a and 12b are schematic cross-sectional representations of
a microelectromechanical component according to another example
embodiment of the present invention.
FIG. 13 is flowchart that illustrates a method for producing a
microelectromechanical component according to yet another example
embodiment of the present invention.
FIGS. 14a-14d are schematic cross-sectional representations of
microelectromechanical components according to further example
embodiments of the present invention.
FIGS. 15a-15c are schematic cross-sectional representations of
microelectromechanical components according to further example
embodiments of the present invention.
FIG. 16 is a schematic cross-sectional view of a
microelectromechanical component according to an example embodiment
of the present invention.
FIG. 17 a schematic cross-sectional view of a
microelectromechanical component according to an example embodiment
of the present invention.
DETAILED DESCRIPTION
FIG. 1 shows a schematic flowchart for explaining a method for
producing a microelectromechanical component according to an
example embodiment of the present invention. In a step S01, a first
wafer having a plurality of microelectromechanical base elements is
provided, in particular produced. The wafer can be in particular a
silicon wafer. The microelectromechanical base elements for their
part can be connected electrically and/or mechanically to the first
wafer, for example by bonding, or can be developed in the first
wafer.
In a step S02, a respective container structure is developed on the
microelectromechanical base elements, preferably at the wafer
level. Alternatively, the base elements can also be separated from
one another together with respective parts of the wafer and be
processed further as chip-scale packages.
In a step S03, an oil or a gel is situated within the container
structures, preferably likewise at the wafer level, e.g., by
filling.
FIG. 2 shows a schematic flowchart for explaining a method for
producing a microelectromechanical component according to another
example embodiment of the present invention. The method according
to FIG. 2 represents a variant of the method according to FIG.
1.
According to the method shown in FIG. 2, the formation S02 of the
container structures includes the following steps: in a step S021,
a polymer layer is formed on the microelectromechanical base
elements. In a step S022, the polymer layer is patterned. In an
optional step S04, the container structure can be sealed,
preferably hermetically. Step S04 is preferably performed if an oil
is used in step S03. When using a gel, it is possible for the
container structure to remain unsealed in some applications, which
can entail advantages, for example a lower weight of the component
and lower technical effort in production. In an optional step S05,
another microelectromechanical element can be electrically
connected to the base element. Subsequently, the individual
finished microelectromechanical components can be separated from
one another.
Preferred developments are explained in the following with
reference to FIGS. 3a-3c, which show already separated and finished
microelectromechanical components 100a-100c for better
comprehensibility. It shall be understood, however, that the
indicated structures and method steps are preferably formed and,
respectively, performed at the wafer level or the
chip-scale-package level.
FIG. 3a shows a microelectromechanical component 100a, which is
producible according to a variant of the method shown in FIG. 2.
According to FIG. 3a, the provided microelectromechanical base
element 110a can be a MEMS pressure sensor having a cavity 130, the
cavity 130 in the case of base element 110a being sealed off from
the environment by a pressure sensor diaphragm 132. Adjacent to
diaphragm 132, on the same side of base element 110a as diaphragm
132, electrical contacts or resistors 134, e.g., piezo resistors,
are situated, which are connected by through-hole contacts 136 to a
back side of base element 110a, that is, an outer side facing away
from the outer side having diaphragm 132.
In step S021, it is possible for a polymer layer 150 to be formed
on the outer side of base element 110a that has diaphragm 132, in
particular prior to forming the contacts or resistors 134, which
polymer layer 150 is subsequently patterned in step S022, for
example by photolithography or etching. The patterning S022 of
polymer layer 150 occurs in particular in such a way that the
remaining parts of polymer layer 150 have a closed annular
structure, which laterally encloses diaphragm 132 and the contacts
or resistors 134 that are formed or are to be formed later.
Disposing S03 oil 40 can occur by filling the annular structure
remaining from polymer layer 150, which thus functions as a
container structure 112a.
In order to prevent the oil 40 from escaping from container
structure 112a, container structure 112a can be subsequently
sealed, preferably hermetically, by a sealing element 114a in the
optional step S04 of the method according to FIG. 2. Sealing
element 114a can be a film or a plate, for example. To connect the
sealing element 114a to container structure 112a, a film can be
used for example as sealing element 114a, which is capable of being
thermally activated, that is, which fuses with adjacent elements,
in this case container structure 112a, when heated.
The film can be made of a plastic or a polymer. The film can also
be a metal foil or be developed from a mixture of a metal and a
polymer. The film can be a pouch foil, for example. The film can be
flexible and thus function as a diaphragm transmitting pressure
from one side to the other.
In the optional step S04 of the method shown in FIG. 2, container
structure 112a including the oil 40 disposed in it can thus be
sealed, for example by applying heat to the film placed on
container structure 112a as sealing element 114a. Alternatively, it
is also possible to use an adhesive technology for connecting
sealing element 114a to container structure 112a for enclosing oil
40, which can be performed for example by using UV light or heat,
for example in order to glue a plate as sealing element 114a to
container structure 112a. Bonding technologies can be used as
well.
Following the optional sealing S04 of container structure 112a, in
a further optional step S05, a further microelectromechanical
element 120, for example an application-specific integrated
circuit, ASIC, can be connected electrically to base element 110a
via through-hole contacts 136.
FIG. 3b shows a microelectromechanical component 100b, which is
producible according to such a variant of the method shown in FIG.
2.
In particular, the additional microelectromechanical element 120
can be designed to evaluate pressure sensor signals of the base
element 110a designed as a pressure sensor. The particularly
compact, layered system made up of container structure 112a, base
element 110a, and the additional microelectromechanical element 120
on the side of base element 110a facing away from diaphragm 132 can
thus form microelectromechanical component 100b, which is
producible using the method described herein. The pressure sensor
signals and/or the signals produced by the additional
microelectromechanical element 120 can be tapped through additional
through-hole contacts 138 through the additional
microelectromechanical element 120.
FIG. 3c shows a microelectromechanical component 100c, which is
producible according to another variant of the method shown in FIG.
2. FIG. 3c illustrates an alternative to the method shown in FIG.
3a, in which the annular structure remaining from polymer layer
150, which functions as container structure 112a, is filled,
entirely or partially, with a gel 42 instead of with oil 40. In
this case, due to the advantageously high viscosity of the gel, it
is possible to do without sealing the container structure 112a, as
shown in FIG. 3c.
FIG. 4 shows a schematic flowchart for explaining a method for
producing a microelectromechanical component according to another
example embodiment of the present invention. The method shown in
FIG. 4 is a variant of the method shown in FIG. 2. The method
according to FIG. 4 comprises the formation S02 of the container
structures and a step S023, in which at least one, preferably one
of each, microelectromechanical or micromechanical structure is
attached on the microelectromechanical base elements. As already
described above, the additional microelectromechanical or
micromechanical structure can be situated in particular by
connecting a second wafer to the first wafer on
microelectromechanical base elements.
FIG. 5a shows a microelectromechanical component 100d, which is
producible according to a variant of the method shown in FIG. 4.
FIG. 5a illustrates in particular a method in which a
micromechanical cap 112b, e.g., a so-called MEMS cap, is disposed
on base element 110a from FIG. 3a as a micromechanical structure,
in particular by bonding the micromechanical cap on the outside of
base element 110a, on which diaphragm 132 is also situated.
Micromechanical cap 112b, which functions as a container structure,
has at least one filler opening 116a through which the oil 40 is
filled into the container structure after attaching S023
micromechanical cap 112b. After the oil 40 has been filled in, the
micromechanical cap 112b can be closed by a film or a plate as
sealing element 114a, as described with reference to FIG. 3a for
example.
Micromechanical cap 112b can be made in particular of glass or
silicon. The second wafer, which is designed for attaching
micromechanical caps 112b on base elements 110a at the wafer level,
can thus be referred to as a glass-cap wafer.
As an alternative to the method described with reference to FIG.
5a, micromechanical cap 112b can be closed in another manner, which
produces a microelectromechanical component 100e shown
schematically in FIG. 5b.
FIG. 5b schematically shows that micromechanical cap 112b has two
filler openings 116b, which are respectively closed by a solder
ball 114b or a metal seal as sealing element. In other words, for
sealing S04 the micromechanical cap 112b functioning as a container
structure, it is possible to perform a method step in which solder
balls are applied specifically onto the filler openings 116b of cap
112b for sealing filler openings 116b. Like the attachment S023 of
micromechanical caps 112b on all base elements 110a, it is also
possible to perform the filling or disposing of oil 40 in cap 112
and the sealing of the filler opening 116b or filler openings 116b
by a film or plate or by soldering balls 114b at the wafer
level.
FIG. 5c explains a production method, which represents a variant of
the method described with reference to FIG. 5a, a
microelectromechanical component 100f being produced in the
process. As in the method described in connection with FIG. 3c, a
gel 42 is used instead of an oil 40 in the method illustrated in
FIG. 5c. The container structure can thus be formed by a
micromechanical cap 112c, which has for example a single,
comparatively large-area filler opening 116c. Filler opening 116c
is used to fill gel 42 into the cavity defined by cap 112c and can
subsequently remain unsealed, which represents a particularly
simple method.
FIG. 6 shows a schematic flowchart for explaining a method for
producing a micromechanical component according to another example
embodiment of the present invention. The method shown in FIG. 6 is
a variant of the method shown in FIG. 2. In the method as shown in
FIG. 6, the formation S02 of the container structure comprises a
formation S024 of a thin-film encapsulation 112d, for example as
shown in FIG. 7 with reference to a microelectromechanical
component 100g.
Thin-film encapsulation 112d can be produced for example by
sputtering or by chemical vapor deposition (CVD). Thin-film
encapsulation 112d can be designed with filler openings 116d, which
can be closed using a film or a plate as sealing element 114a, for
example as described with reference to FIG. 3a.
FIG. 8 shows a schematic flowchart for explaining a method for
producing a micromechanical component 100h; 100i; 100k; 100l
according to further example embodiments of the present invention.
The method as shown in FIG. 8 is a variant of the method as shown
in FIG. 1 and differs from the latter in particular in that in a
step S06 an application-specific circuit, ASIC 122a; 122b is
disposed within the oil 40 or the gel 42 within the container
structure. The method as shown in FIG. 8 is explained in more
detail in the following with reference to FIGS. 9a-9d. It shall be
understood that step S02 of the method shown in FIG. 8 can be
performed as explained with reference to FIG. 2, 4, or 6. The
method according to FIG. 8 can likewise have the optional step S04
and S05, as was explained e.g., with reference to FIG. 2.
FIG. 9a illustrates a variant of the method according to FIG. 8 and
shows a micromechanical component 100h, in which on top of a base
element 110a, as described with reference to FIG. 3a, a container
structure 112a having a sealing element 114a is developed, as
likewise described with reference to FIG. 3a. Within oil 40 and
within container structure 112a, an ASIC 122a is disposed and is
connected electrically and mechanically via contacts of ASIC 122a
with the contacts or resistors 134 of base element 110a.
As illustrated with reference to FIG. 9b, a microelectromechanical
component 100i can also be produced in that the ASIC 122a is
disposed for example within the micromechanical cap 112b of
microelectromechanical component 100d, as described with reference
to FIG. 9a. In particular, it is possible first to bond ASIC 122a
to the contacts or resistors 134 of base element 110a and thereupon
to bond micromechanical cap 112b around ASIC 122a onto base element
110a. Subsequently, cap 112b can be filled with oil 40 and sealed
using sealing element 114a, as described for example with reference
to FIG. 5a. Alternatively, filler opening 116 of cap 112b can also
be sealed using solder balls, for example as described with
reference to FIG. 5b.
Within the container structure, it is also possible to dispose an
ASIC 122b, as also illustrated by FIG. 9c, which has a block-shaped
bulge, ASIC 122b being situated on base element 110a in such a way
that the bulge comes to lie exactly above diaphragm 132 of base
element 110a and thus produces another cavity 140 directly adjacent
to diaphragm 132. For pressure equalization, for example, channels
142 can be formed through ASIC 122b. As indicated in FIG. 9c, these
channels 142 can be developed having a small diameter so that a
pressure equalization can occur between cavity 140 and the oil 40
surrounding ASIC 122b, but that at the same time only small
quantities of oil 40 are able to enter cavity 140.
According to FIG. 9c, a container structure 112a as well as an
associated sealing element 114a is developed in component 100k, as
described with reference to FIG. 3a. It goes without saying that it
is also possible to use all other methods and variants described
above for forming a container structure on the base element.
FIG. 9d shows the case for example in which ASIC 122b is formed by
the container structure as described in FIG. 3c, that is, filled
with a gel 42 and unsealed.
Of course, it is also possible to situate any other ASICs,
surrounded by a gel 42, in an unsealed container structure
112a.
FIGS. 10a-10c show schematic sectional illustrations of a
microelectromechanical component 100m according to yet another
example embodiment of the present invention.
FIG. 10a shows a schematic top view onto component 100m, FIG. 10b a
cross section along the line A-A in FIG. 10a, and FIG. 10c a cross
section along the line B-B in FIG. 10a.
Component 110m is a variant of component 100d or of component 100e
and differs from these in that it has a container structure 112e
instead of container structure 112b. Container structure 112e
differs from container structure 112b in the shape of filler
opening 116e of container structure 112e, which, as shown in FIG.
10a, is designed to be U-shaped. The area of the cover of container
structure 112e that is enclosed on three sides by the U-shape is
thus designed as a cantilever 117. The size of filler opening 116e
is exaggerated in FIGS. 10a-10c.
FIGS. 11a-11c show schematic cross-sectional illustrations of
component 100m analogous to FIG. 10c, i.e., along the sectional
line B-B in FIG. 10a, for explaining a production method for
microelectromechanical component 100m. Component 100m can first be
developed as described with reference to component 100d or
component 100e. For disposing S03 oil 40 in container structure
112e, it is then possible to move a filler nozzle 180 in the
direction of filler opening 116e, as illustrated in FIG. 11a. Using
filler nozzle 180, cantilever 117 can be pressed in the direction
of base element 110a so that an access is created for oil 40 from
filler nozzle 180 into the area comprised by container structure
112e (FIG. 11b). After disposing S03 oil 40, filler nozzle 180 is
again pulled away from base element 110a (FIG. 11c).
Due to the elastic properties of the material of container
structure 112e, which is advantageously formed, e.g., from silicon,
cantilever 117 thereupon closes automatically. Cantilever 117 thus
functions as an open/closed valve. Filler opening 116e is adjusted
to oil 40 in such dimensions that when cantilever 117 is closed the
oil 40 remains in container structure 112e due to the tight filler
opening 116e and the surface tension of oil 40. An additional
sealing of the filler opening 116e can thus be omitted. Developing
component 100m in the manner described, in particular situating S03
oil 40, can be performed for separated components, but is
advantageously performed at the wafer level for a multitude of
components 100m simultaneously.
FIGS. 12a and 12b show schematic cross-sectional illustrations of a
microelectromechanical component 100n according to another example
embodiment of the present invention.
Microelectromechanical components 100n is a variant of
microelectromechanical component 100m and differs from the latter
in that container structure 112e is not situated directly on base
element 110a itself, but rather on a wafer 160 and surrounds base
element 110a, which is likewise situated on wafer 160.
Optionally, another microelectromechanical element electrically
connected to base element 110a, for example an ASIC 124, can be
situated within container structure 112e. As indicated in FIG. 12a,
container structure 112e can be likewise filled with oil 40 as
described with reference to FIGS. 11a-11c. Optionally, as shown in
FIG. 12b, filler opening 116e can be sealed by a sealing element
114d, for example by a porous membrane.
The microelectromechanical component 100n shown in FIG. 12a can
represent a wafer system, i.e., a system of a multitude of base
elements 110a, ASICs 124 and container structures 112e on one and
the same wafer 160. Alternatively, the microelectromechanical
component 100n shown in FIG. 12a can also be completed, in
particular filled with oil 40, at the package level, that is, e.g.,
after separation.
FIG. 13 shows a schematic flowchart for explaining a method for
producing a microelectromechanical component 100o; 100p; 100q; 100r
according to further example embodiments of the present
invention.
The method as shown in FIG. 13 is a variant of one of the methods
shown in FIGS. 1-9d as described above and differs from the latter
in that in a step S07 another (e.g., a second) container structure
113a; 113b; 113c is disposed around base element 110a with the
attached container structure 112a, preferably at the wafer level,
and that in a step S08, preferably at the wafer level, another oil
or gel 44 is disposed within the additional container structure
113a; 113b; 113c, as illustrated below with reference to FIGS. 14a
through 14d.
FIGS. 14a-14d illustrate furthermore separated
microelectromechanical components 100o-100r according to example
embodiments of the present invention. Microelectromechanical
components 100o-100r can also be situated in a multitude
simultaneously on a common wafer 160 (e.g., up until separation)
such that FIGS. 14a-14d also illustrate wafer systems according to
example embodiments of the present invention.
In a variant illustrated with reference to FIG. 14a of the method
according to FIG. 13, a container structure 113a is disposed around
microelectromechanical component 100a, as was described with
reference to FIG. 3a, on wafer 160, on which component 100a is also
situated. As described with reference to FIG. 3a in relation to
container structure 112a, container structure 113a can also be
formed by patterning a polymer layer, in particular by
photolithography and/or etching. Alternatively, however, other
container structures, for example container structures 112b made of
micromechanical caps, can also be disposed around a
microelectromechanical component 100a on wafer 160.
In step S08, the additional oil or gel 44 is disposed in the
additional container structure 113a. Especially if an oil is used,
the additional container structure 113a can be subsequently closed
as described above with reference to container structure 112a,
i.e., in particular by a film or plate as sealing element 114a, by
solder balls 114b, and so on.
In the method according to FIG. 14a, an ASIC 124, which is
electrically connected to microelectromechanical component 100a,
e.g., via through-hole contacts or buried conductors 146 through
wafer 160 and/or bonding wires 142, is disposed on an outer side of
wafer 160, which faces away from the outer side of wafer 160 on
which microelectromechanical component 100a and the additional
container structure 113a are situated. The system made up of wafer
160, component 100a or components 100a, container structure 113a or
container structures 113a, and ASIC 124 or ASICs 124 connected
thereto, as shown in FIG. 14a, can in turn be called a wafer system
100o or, following separation, a microelectromechanical
component.
In a variant illustrated in FIG. 14b of the method according to
FIG. 14a, component 100c according to FIG. 3c is used instead of
component 100a according to FIG. 3a. Due to the inner cohesion and
preferably greater viscosity, the additional gel 44, as shown in
FIG. 14c, can have a boundary layer with respect to gel 42 within
container structure 112a of component 100c. The system made up of
wafer 160, component 100c or components 100c, container structure
113a or container structures 113a, and ASIC 124 or ASICs 124
connected thereto, as shown in FIG. 14b, can in turn be called a
wafer system 100p or, following separation, a
microelectromechanical component.
In a variant illustrated by FIG. 14c of the method according to
FIG. 14b, ASIC 124 is situated on the same outer side of wafer 160
as microelectromechanical component 100a and is electrically
connected to component 100a for example by bonding wires 142. A
container structure 113a is situated around component 100a and ASIC
124, in which the additional gel 44 is situated, for example as
described with reference to FIG. 14a. Thus, the additional gel 44
protects also the bonding wires 142 between ASIC 124 and component
100a against environmental influences. The system made up of wafer
160, component 100a or components 100a, container structure 113a or
container structures 113a, and ASIC 124 or ASICs 124 connected
thereto, as shown in FIG. 14c, can in turn be called a wafer system
100o or, following separation, a microelectromechanical
component.
In wafer system 100o according to FIG. 14a, it is also possible for
base element 110a and ASIC 124 to be situated on the same side of
wafer 160.
In a variant illustrated in FIG. 14d of the method according to
FIG. 14b, a container structure 113c is situated on wafer 160,
which has two chambers separated from each other, component 100a
and additional gel 44 being situated in a first of the two
chambers, and ASIC 124 and yet another gel 46 or oil being situated
in a second of the two chambers. The two chambers can have a common
wall, under which connecting lines can run for electrically
connecting component 100a and ASIC 124, e.g., within wafer 160.
Technically, container structure 113c can be produced just as
described with reference to container structure 112a. It is
possible for an oil to be disposed in both chambers of container
structure 113c or for a gel to be disposed in both chambers of
container structure 113c. Each of the chambers can be sealed by a
sealing element, as described above, in particular if an oil was
disposed in the respective chamber.
FIGS. 15a-15c illustrate that it is possible to use container
structures, as were described above, e.g., container structures
112a made from a polymer layer, also to keep an epoxy resin (or
another type of mass), which is used on a surface of a
microelectromechanical base element 110a, away from an area, e.g.,
a diaphragm 132, on base element 110a that is to be kept clear.
This can be done by an annular container structure 112a against a
surrounding epoxy resin (or another type of mass), as shown in FIG.
15a, or by an annular container structure 112a against an epoxy
resin (or another type of mass) present on one side, as shown in
FIG. 15b, or by a separating structure 112f developed as a single
wall, as shown in FIG. 15c. Separating structure 112f can be
produced in the same manner as the container structures, in
particular from a polymer layer 150.
FIG. 16 shows a schematic cross-sectional view of a
microelectromechanical component 100s according to an example
embodiment of the present invention, which can likewise be produced
using one of the described production methods. Component 100s is a
variant of component 100d, which differs from component 100d in
that a piezoelectric resistor 152 disposed within container
structure 112a is electrically connected by a buried conductor 148
to a bonding pad 149 situated outside of container structure 112b,
but on the same surface of base element 110s of component 100s as
container structure 112b. Bonding pad 149 is electrically connected
to wafer 160 via a bonding wire 142. The bonding pad, bonding wire
142, and base element 110s are encapsulated by a mass 115a, e.g.,
an epoxy resin. Container structure 112b thus separates the oil 40
disposed to protect diaphragm 132 from mass 115a.
FIG. 17 shows a schematic cross-sectional view of a
microelectromechanical component 100s100t according to an example
embodiment of the present invention. In component 100s100t, a base
element 110a is provided with a separating structure 112f, as shown
in FIG. 15c, and is disposed within a cavity 170 that is developed
in such a way that an inner side wall 172 of cavity 170 together
with separating structure 112f forms a container structure 112g. A
gel 42 is disposed within container structure 112g, which protects
diaphragm 132 of base element 110a against environmental
influences.
On a side of separating structure 112f facing away from gel 42,
another mass 115b, for example another gel or an epoxy resin, is
disposed likewise within cavity 170, which is kept away from gel 42
by separating structure 112f. A bonding pad 149 and a bonding wire
142 can be encapsulated in mass 115b. Cavity 170 can be sealed by a
sealing element 114c, which can be developed for example like
sealing element 114a.
In all methods described above, the base element can also be
another microelectromechanical component, other than a MEMS
pressure sensor, for example an application-specific integrated
circuit. Instead of protecting a diaphragm of a MEMS pressure
sensor, the oil or the gel can protect a contact or a through-hole
contact of the application-specific integrated circuit against
environmental influences. Contacts on a side or surface of the base
element or the wafer that are not protected by the container
structure or the oil or gel disposed therein can be protected by an
underfill for example.
In all cases in which a micromechanical or microelectromechanical
structure for forming the container structure is connected to the
base element, this structure can have a cantilever, in particular
in its cover, via which the structure can be filled with the oil or
the gel after being connected to the base element, and which due to
restoring forces subsequently swings back into a position in which
the oil or the gel remains enclosed within the structure. In such a
variant, a separate sealing element can be omitted, which reduces
the technical expenditure. Such variants having a cantilever can be
developed as described above with reference to FIGS. 10a-12b.
* * * * *